Production of globular regenerated cellulose particles



March 29, 1949. o. A. BATTISTA 2,465,343 PRODUCTION OF GLOBULAR REGENERATED CELLULOSE PARTICLES Filed Feb. 15, 1947 INVENTOR. ORLANDO A. BA 77'/$TA -'."gl0bul'ar particles Patented Mar. 29, 1949 PRODUCTION-OF GLOBULAR REGENERATED CELLULOSE PARTICLES Orlando. A. Battista, Swarthmore,Pa.,-assignorto American 'Viscose Corporation, Wilmington, Del, 'acorporation of Delaware Application February 15, IMZBeriaITNo. 728.9112

- Claims.

This invention relates "to the production of of regenerated cellulose, particularly from viscose.

Methods'that .have heretofore been employed for making globular particles from viscose resulted generally in products which not only were "farfromsphericity but were marred by numerous checks and fissures resulting from the inability :to prevent the development of gases within the g'lobules during regeneration and the inability :to prevent irregular shrinkage during regeneration,,subsequent wet process, and drying of the globules.

- In accordance with the present invention these difficulties are substantially completely avoided. 'This is accomplished by limiting the contact of the freshly formed globules with the acid regeneratingbath (into whichthey .fallin droplets) to that which merely forms a .thin skin upon the outer surface of the globule and which is inadequate to develop any as bubbles within the'globules. After the limited contact in theacid bath, the globules'having the thin "skin which maintains the spherical structure are introduced .into a heated liquid of non-solvent non-precipitating character in which coagulation and regeneration of the globules are completed. Suitable liquids for this purpose which are incapable of dissolving the granules are hot water orlhot mineral oil at a temperature below the boiling, point of water.

.After theglobules are taken from the heated liquid, the by-products of regeneration, such as alkalineandsulfur compounds, arein a watersoluble state and are merely leached out by introducing theglobulesinto water for the desired period of time. Thereafter, the globules may .be'dried or, before drying, they maybesoaked in .a plasticizer, such as vglycerine, when a softenedproduct is desired. Shrinkage of any substantial extent can only occur during the drying step of this proceduresince the contact of the globuleswith acid is restricted to a minimum and the globules are maintained in waterswelled condition thereafter until the drying stage. .It has been found that the shrinkage that occurs during the drying of the globules formedin accordance with the procedure of this invention is remarkably uniform in character so that they .undergo .little change in their original shape other than a diminution in size during the drying.

The original shape of the globules formed depends upon the height "from which the viscose droplets are allowed to fall into the acid bath. If a substantially spherical shape of definite diameter is desired-the viscose should be dropped from aheight between 'four'andcsix feet above the level of the acid bath, the less viscous the viscose, the lower the height that should be used.

If greater dropping 'heights "are used, the size ofthe droplet falling from-the dropping orifice or jet does not "determine the ultimate size of the product as,"in"such'case, theytend to disrupt into numerous smaller particles which may'have various sizes and, intheiextreme of conditions, "a' powdered product results.

4. These tubes'have orifices of any conventional character adapted to'the formation of droplets under the hydrostatic head within the hopper, or under'the application of any other hydraulic force. A receptacle 5 forithe acid bath is arranged beneath the hopper to receive the 'droplets and has a sloped bottom 6 terminatingv in an opening 1 'of small diameter to allow passage of the skinned globules onto the top surface of a foraminous'belt 8, such as of wire screen. A pair of inclined deflectors 9 and lllmay be arranged in advance of the opening I to disrupt any liquid stream flowing therefrom before it goes beyond'the belt. A drainbox H is arranged beneath the upper course of the belt to catch the acid passing through the'belt and this acid may be 'recirculatedtothe receptacle 5 by means of pump l2. Rolls "l3 drive the belt 8 which dumps the globules thereon into a receptacle l4 containing heated liquid such as mineral oil or 1 water below 99 C. A chain conveyor l5 having projecting transverse slots I6 is arranged within the receptacle at an inclination so that it serves to carry the globules therefrom to the neXt receptacle ll containing water in which the globules are leached. A similar inclined conveyor may be arranged in'this receptacle for carrying the globules therefrom to the next stage of treatment which may be'that of drying or that of soaking in a plasticizer, such as glycerine, after which drying may be effected.

The'depth of the acid bath in the receptacle 5 mayvary from 3 to '12 inches and the slope of the bottom 6 is so selected with relation to the liquid depth that the time required for the globules to .pass :throughlthe acid bath is only that which forms askin without forming .gas bubbles Within the globules. The maximum permissible time of this passage depends mainly on'the concentrationo'f the acid. Where a bath having a sulfuric acid concentration of 10% .is used, .a passage of one minute .is satisfactory, while a longer time of passage is permissible with a weaker acid .bath, .and vice versa. .Sulfuric acid baths of"? to 12% concentration may be used.

The final products which may be of any size up to the order of A; inch in diameter approach true sphericity and are substantially free of checks, fissures, bubbles, creases and wrinkles. The unplasticized products are hard and have a. high dielectric constant. 7 Because of this characteristic and the fact that the products are highly resistant to hydrocarbon oils they may be used in conjunction with such oils for cooling electrical equipment, such as transformers. They may also be used in lightning arresters and as line protective means, for example, fuse elements, particularly in circuit breakers. The unplasticized products may be coated with moistureproofing and chemically resistant compositions where their use would involve prolonged contact with moisture, acids, alkalies, or other corrosive fluids. The plasticized products are of use where flexibility is desirable. V

It is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

1. The method of making granular particles comprising regenerated cellulose comprising the steps of allowing droplets of viscose to fall into an acid bath, removing the formed granules of viscose from the bath after a thin skin has been formed thereon as a result of the precipitating action of the acid bath but before gas bubbles are formed within the granules, and regenerating the superficially precipitated granules in a hot substantially non-acid bath of a liquid incapable of dissolving the granules.

2. The method of making granular particles comprising regenerated cellulose comprising the steps of allowing droplets of viscose to fall into an acid bath, removing the formed granules of viscose from the bath after a thin skin has been formed thereon as a result of the precipitating action of the acid bath but before gas bubbles are formed within the granules, regenerating the superficially precipitated granules in a hot substantially non-acid bath of a liquid incapable of dissolving the granules and then leaching the granules.

3. The method of making granular particles comprising regenerated cellulose comprising the steps of allowing droplets of viscose to fall from a height of about 4 to 6 feet into a sulfuric acid regenerating bath, removing the formed granules of viscose from the bath after a thin skin has been formed thereon as a result of the precipitating action of the acid bath but before gas bubbles are formed with the granules, regenerating the superficially precipitated granules in a hot substantially non-acid bath of a liquid incapable of dissolving the granules- 4. The method of making granular particles comprising regenerated cellulose comprising the steps of allowing droplets of viscose from a height of about 4 to 6 feet into a sulfuric acid regenerating bath, removing the formed granules of viscose from the bath after a thin skin has been formed thereon as a result of the precipitating action of the acid bath but before gas bubbles are formed with the granules, and regenerating the superficially precipitated granules in a hot bath of mineral oil.

5. The method of making regenerated cellulose globules approaching sphericity in shape comprisin the steps of allowing viscose to fall in the form of individual drops from a height of about 4 to 6 feet into a sulfuric acid regenerating bath of about 7 to 12% concentration, removing the formed globules from the bath after a thin skin has been formed thereon but before gas bubbles are developed within the globules, and regenerating the superficially precipitated globules in a hot substantially non-acid bath of a liquid incapable of dissolving the globules.

6. The method of making regenerated cellulose globules approaching sphericity in shape comprising the steps of allowing viscose to fall in the form of individual drops from a height of about 4 to 6 feet into a sulfuric acid regenerating bath of about 7 to 12% concentration, removing the formed globules from the bath after a thin skin has been formed thereon but before gas bubbles are developed with the globules, and regenerating the superficially precipitated globules in a hot mineral oil bath.

7. The method of making regenerated cellulose globules approaching sphericity in shape comprising the steps of allowing viscose to fall in the form of individual drops from a height of about 4 to 6 feet into a sulfuric acid regenerating bath of about 10% concentration, removing the formed globules from the bath after about one minute, regenerating the superficially precipitated globules in a hot substantially non-acid bath of a liquid incapable of dissolving the globules.

8. The method of making regenerated cellulose globules approaching sphericity in shape comprising the steps of allowing viscose to fall in the form of individual drops from a height of about 4 to 6 feet into a sulfuric acid regenerating bath of about 10% concentration, removing the formed globules from the bath after about one minute, and regenerating the superficially precipitated globules in a hot mineral oil bath.

9. The method of making regenerated cellulose globules approaching sphericity in shape comprising the steps of allowing viscose to fall in the form of individual drops from a height of about 4 to 6 feet into a sulfuric acid regenerating bath of about 10% concentration, removin the formed globules from the bath after about one minute, regenerating the superficially precipitated globules in a hot mineral oil bath, leaching the globules in water, and subsequentially dry ing them.

10. The method of making regenerated cellulose globules approaching sphericity in shape comprising the steps of allowing viscose to fall in the form of individual drops from a height of about 4 to 6 feet into a sulfuric acid regenerating bath of about 10% concentration, removing the formed globules from the bath after about one minute, regenerating the superficially precipitated globules in a hot mineral oil bath, leaching the globules in water, introducing the globules While wet into a bath of plasticizer, and drying them.

ORLANDO A. BATTISTA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Peschardt July 9, 19 46 Certificate of Correction Patent No. 2,465,343.

ORLANDO A. BATTISTA It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 3, line 62, after the word viscose insert to fall and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 11th day of October, A. D. 1949.

THOMAS F. MURPHY,

' Assistant Gammissioner of Patents.

March 29, 1949. 

